This invention relates to treating fibrous materials for subsequent processing. This invention also relates to cleaning, fine opening and orienting fibrous materials in the production of a web thereof. More particularly, it relates to cleaning and orienting fibrous materials in the high capacity production of a web. Still more particularly, it relates to an apparatus and method applicable to cotton, synthetic fibers, cotton blends, wool, and other textile fibers.
In the past, the production of nonwoven cotton batts, for example for subsequent production of nonwoven fabrics or sliver, has commonly entailed a process wherein the material supplied to an ordinary nonwoven finisher carding machine has undergone scouring and bleaching (hereinafter referred to as "chemical treatment") by means of a batchkier technique. The product of this chemical treatment constitutes a wet cake of fiber that must be broken up to dry. Wet picking practices undertaken in this connection often form non-uniform, stringy and twisted elements which, in turn, result in a non-uniform web emanating from the carding machine having varying amounts of neps.
This natural result of the conventional chemical treatment can be avoided by providing a continuous scouring and bleaching operation for preparation of the material to be supplied to the finishing cards. Such a continuous scouring and bleaching operation would allow for treatment and drying of a web on a continuous basis, thereby avoiding the wet-picking procedures which form the stringy, twisted elements.
However, in order to render a continuous chemical treatment operation economically feasible, it is necessary that the web be supplied to the scouring and bleaching equipment at a relatively high rate, such as several thousand pounds of material per hour, e.g., about seven thousand pounds per hour or more. It is also desirable that the web so supplied be reasonably clean, of appropriate area density, and uniformly constituted and free of neps to an acceptable degree.
It is known that conventional carding machines are capable of producing a cotton web of relatively low weights per yard, or low area densities. Since the extent of cleaning is, to a great degree, a function of web weight, the greater the degree of attenuation of the web, the cleaner it will be. However, when conventional carding machines are operated to produce webs of the desired low area density, production capacity is significantly sacrificed. Indeed, production capacity of seventy pounds per hour is considered high for conventional carding machines; it is generally, on the average, considerably lower. Experimental runs at up to three hundred pounds per hour capacity have been conducted with conventional carding machines, but web uniformity and cleanliness were detrimentally affected to the point of producing a commercially unacceptable product.
The unfeasibility of using the common carding apparatus for high capacity production of an acceptable web stems from its inherent structural characteristics.
Conventional carding machines, as they have been in use for many years, and as are still predominantly in use, consist essentially of a lickerin to pluck small tufts of fiber from a batt of partially opened fibers, a carding cylinder onto which the fibers are deposited by the lickerin, a plurality of flat bars, the "revolving flats", which surround about one-third of the peripheral surface of the carding cylinder, and a doffer which removes the fibers from the cylinder. The revolving flats have a needle or wire clothing surface, similar to that of the carding cylinder. The flats, which are relatively motionless with respect to the cylinder, move only a few inches per minute for the purpose of being cleaned. The carding cylinder, which, in the conventional card is ordinarily about 50 inches in diameter, rotates at a peripheral speed of about 2000 to 4000 feet per minute as it carries the fibers past the revolving flats.
During the carding process, the needles of the revolving flats collect fibers from the carding cylinder and become loaded and relatively ineffective for about 60 percent of the working cycle. The unopened fibers collected by the flats amount to about from two to five percent of the total fibrous material fed to the machine. These fibers, known as "flat strips," are generally disposed of as waste. In addition, loading of the flats also forces the fibers on the cylinder down into the cylinder clothing, causing impacting, and increasing the amount of material wasted by about another one percent. It is thus seen that a number of factors combine to contribute to the limitation on the output capacity of the convention carding apparatus. A problem which in recent years, has achieved prominence is that the structure and accompanying mechanism of the revolving flats are such that it is generally difficult to provide adequate cover for the entire machine to avoid contaminating the atmosphere in the vicinity of the machines with flying dust and fibers. As already mentioned, in the case of the conventional carding apparatus, the main carding cylinder itself generally rotates at a peripheral speed of about 2000 to 4000 feet per minute as it carries the fibers past the revolving flats. At this speed, depending upon the desired weight per unit length of the delivered sliver, the output of the card may vary from about 10 to about 50 or 60 pounds of carded cotton per hour.
From the foregoing, it will be apparent that utilization of conventional carding machines to continuously supply a web for continuous chemical treatment, as discussed above, has not been entirely feasible. On the one hand, if a high mass rate of feed for continuous chemical treatment were desired by a mill, there would be a need for a large capital investment in a great number of carding machines to operate simultaneously to yield the required web supply. On the other hand, if fewer machines were operated, this would require settling for a low supply rate. Such a sacrifice of input capacity to the chemical treatment operation would dominate the entire run thereafter, thus rendering the economics of continuous scouring and bleaching marginal at best. If a middle ground were to be chosen so that an intermediate number of conventional machines were simultaneously operated at higher than normal production rates, web uniformity and cleanliness would be sacrificed, while only partially reducing the large capital investment in carding machines.
It is, therefore, desirable to provide a novel apparatus and process, particularly applicable to cotton, but not limited thereto, whereby reasonably clean webs of appropriate area density and uniformity constituted to a commercially acceptable degree, can be produced at high capacity, e.g., up to about 700 pounds per hour or higher.
Attempts have been made over the years to improve various aspects of the carding operation. However, these attempts appear to have been restricted to solving isolated difficulties rather than to produce a comprehensively new carding apparatus which solved a broad spectrum of difficulties, such as fiber damage, non-uniformity of the carded web, environmental contamination, low output, and the like.
One proposed device, stated to improve the quality of the carded fibers, was disclosed in 1935 in U.S. Pat. No. 2,014,673. This device essentially comprised two cylinders mounted adjacent one another for rotation on parallel axes. The first cylinder, to which fibers to be carded, cleaned, or opened were fed, was provided with peripheral teeth tangent to the surface of the cylinder. Teeth of this design were stated to separate and align the fibers without damaging them. The fibers were removed from the teeth of the first cylinder by projecting teeth mounted on the periphery of the second cylinder. Instead of revolving flats, the cylinders were provided with tightly fitting cylindrical covers on the upper portions of their peripheries and with grid bars below for removing trash and other foreign matter. The fibers were removed from the second cylinder by means of a current of air. It is interesting to note further that this disclosure shows a stripping action where the rake angles shown on the teeth of the "feed" roll and the "stripping" roll are such that the stripping roll must either rotate more slowly and in an opposite direction to the feed roll, or the stripper roll must rotate in the same direction as the feed roll, in order to strip the fiber from the feed roll. It should also be noted that U.S. Pat. No. 2,041,673 stipulates that the teeth of the stripping roll sweep through the channels of the teeth in the feed roll.
Another proposal for eliminating the revolving flats and to improve the quality of the carded fibers was disclosed in U.S. Pat. No. 2,879,549. This proposal comprised substituting a tightly-fitted cover plate over the carding cylinder and coating the concave inside surface of this cover plate with a granular, abrasive material. The mass of fibers, as it was carried around by the carding cylinder, was subjected to the abrasive and retarding action of the granular surface which caused the fibers to be straightened and attenuated. Although this device was stated to produce a batt or sliver with less waste and containing fewer neps, as well as minimizing the delivery to the surrounding atmosphere of dust and other fibers, it nevertheless was still basically dependent on a conventional carding cylinder, operating at its usual peripheral speed of about 2000 to 4000 feet per minute. Although this device was also stated to result in a higher output of a better quality fiber, this increase in output actually represented a minimization of waste within the machine itself rather than the result of a higher throughput capacity. In other words, the increased output was a result of the substantial elimination of the "flat strips" which constituted unopened fibers collected by the conventional revolving flats, as well as the waste resulting from loading of the cylinder clothing itself. The reduction in neps was the result of further minimizing the loading of the teeth on the revolving cylinder itself.
An improvement over the granular card was disclosed in U.S. Pat. No. 3,604,062 which, in one aspect, substituted a concave plate having a plurality of teeth on its inside concave surface, for the abrasive-coated plate of U.S. Pat. No. 2,879,549. The carding cylinder itself was provided with teeth having a forward rake angle, while the teeth on the inner surface of the stationary concave cover were pitched in the opposite direction. In the conventional revolving flat type of cards, as well as those having roller tops, the teeth on the flats or rolls do not present a continuous opposing carding surface to the teeth on the main cylinder. Therefore, in the cases of revolving flat or roller type cards, the carding action is accomplished only at intermittent tangent lines along the moving cylindrical surface. As regards the granular type card, the stationary surface is made up of granules which are irregular in shape, have little depth, and are of a relatively smooth surface, all of which combine to result in a general diminishing of carding uniformity and efficiency. In the carding apparatus of U.S. Pat. No. 3,604,062, carding takes place in a uniform manner over the entire surface with the result that more actual carding points are provided. Another advantage claimed for the machine of U.S. Pat. No. 3,604,062 was that it also could be used in conjunction with the conventional revolving flat type cards, or with roller type cards, where the fibers are first carded by the revolving flats or rollers covering a portion of the carrying surface of the main carding cylinder, and the finished carding could be accomplished by placing a smaller stationary plate adjacent the carding surface of the main cylinder immediately following the revolving flats or worker roll. It was thus possible to further card the fibers without the necessity of transferring them to a different machine. As a result of this invention, it was possible to produce a carding machine having a main cylinder of smaller diameter than those which had been conventionally used. Another advantage claimed for the apparatus of the patent was greater durability as a result of using the metallic card clothing. A further advantage of this machine was stated to be the ability to use only a single lickerin cylinder and a single doffer. Such a machine, however, still only had a production capacity varying from 10 to 80 pounds per hour, depending on the machine adjustment. This output was not significantly different from that of the conventional card and was still not satisfactory where a high, continuous output is required for supplying a high quality batt or web directly to the chemical treating operation or to the spinning process.
U.S. Pat. No. 3,081,499 disclosed apparatus comprising a train of three parallel, toothed cylinders all of equal diameter. The first two cylinders rotated in the same direction (e.g., counterclockwise) while the third rotates in the opposite direction. Each cylinder was provided with teeth which are disclosed to be substantially radial, that is, the forward faces of the teeth have substantially a zero rake angle in that they are straight, linear extensions of a radius of the cylinder. The first cylinder constituted the breaker, while carding was accomplished by the teeth in the nip between the first two cylinders. Each of the first two cylinders was provided with a smaller, clearer roll. The third cylinder provided a condensing action to densify the attenuated fibers and deliver them to a conveyor in the form of a self-sustaining web. One of the advantages asserted by the patent was the greatly increased capacity of the carding unit as regards the quantity of fiber which could be successfully passed through the machine. Thus, the patent points out, that in a conventional carding machine where the main carding cylinder has a diameter of about 50 inches and is rotated at about 165 rpm, established practice calls for a feed rate of about 10 pounds per hour of cotton. Furthermore, the conventional carding machines described in the background of U.S. Pat. No. 3,081,499, because of the loading of the flats, require continuous shutdowns over a day's operation for cleaning, with the frequency of shutdowns increasing as attempts are made to increase the speed of operation. According to the patent, on the other hand, the disclosed carding machine can be maintained at a continuous throughput of 60 pounds per hour of cotton.
The search has continued, therefore, for processes and apparatus able to provide a continuously high throughput, e.g., 700 pounds per hour or more, while achieving an acceptable degree of cleanliness and uniformity (fine opening and orientation), with a substantial absence of formation of neps.